FIGURE 1.

SARS-CoV S-protein-mediated pseudovirus entry is blocked by cathepsin L inhibitor. HEK293T cells were transfected with plasmids encoding human ACE2 or the HIV-1 receptors CD4 and CXCR4, replated, and infected with GFP-expressing MLV virus pseudotyped with the SARS-CoV S protein or HIV-1 envelope glycoprotein (SARS/MLV or HIV-1/MLV, respectively). Target cells were preincubated for 3 h with indicated concentrations of protease inhibitors (A) or cathepsin inhibitors (B) and incubated for 5 h with the indicated pseudoviruses and inhibitors. Infected cells were trypsinized 48–60 h later, and GFP expression was measured by flow cytometry. C, fluorescent micrographs of cells infected in the presence and absence of 10 μm cathepsin L inhibitor. Abbreviations used are: Phsdn, phosphoramidon; Pep A, pepstatin A; Cath L, cathepsin L.